docs: reorganize into project/ + reference/, expand Storybook Foundations

Move working docs (backlog, prd, roadmap) under docs/project/ and durable
docs (architecture ADRs, guides, audits) under docs/reference/; add a
docs/README.md index. Update every path reference in code comments, CLAUDE.md,
READMEs, and the new-ssp skill. Expand the Storybook Foundations curriculum
(Overview, BDD, i18n; rename Layers→Domain-Driven Design) and reorder the sidebar.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/registratie/application/big-profile.store.ts

@@ -21,7 +21,7 @@ type Err = Error | undefined;
  * The dashboard data now comes from ONE screen-shaped ("BFF-lite") call that
  * returns registration + person + server-computed `decisions`. One request → one
  * consistent snapshot, instead of stitching three independently loading/erroring
- * resources together client-side. See docs/architecture/0001-bff-lite-decision-dtos.md.
+ * resources together client-side. See docs/reference/architecture/0001-bff-lite-decision-dtos.md.
  */
 @Injectable({ providedIn: 'root' })
 export class BigProfileStore {

src/app/registratie/contracts/brp-address.dto.ts

@@ -3,7 +3,7 @@
  *
  * In production this is GENERATED from the OpenAPI/TypeSpec spec and served by our
  * own backend, which talks to the BRP behind an adapter. The frontend never sees
- * the BRP's own wire format. See docs/architecture/0001-bff-lite-decision-dtos.md.
+ * the BRP's own wire format. See docs/reference/architecture/0001-bff-lite-decision-dtos.md.
  *
  * "Geen adres bekend" is a first-class outcome (`gevonden: false`), not an error —
  * the wizard falls back to manual entry (PRD §7). Slice 1 ships only the happy

src/app/registratie/contracts/dashboard-view.dto.ts

@@ -10,7 +10,7 @@
  * In production these types are GENERATED from the OpenAPI/TypeSpec spec (one
  * source of truth for both sides), and the `decisions` block is computed BY THE
  * BACKEND — never recomputed on the client. The frontend renders decisions; it
- * does not own the rules. See docs/architecture/0001-bff-lite-decision-dtos.md.
+ * does not own the rules. See docs/reference/architecture/0001-bff-lite-decision-dtos.md.
  *
  * One screen-shaped call replaces the previous three (BIG-register + BRP + …),
  * so the page always sees one consistent snapshot instead of three independently

src/app/registratie/ui/aanvraag-block/aanvraag-block.stories.ts

@@ -25,7 +25,7 @@ const meta: Meta<AanvraagBlockComponent> = {
   parameters: {
     // Structural: app-aanvraag-block's host sits between the keuzelijst <ul> and its <li>
     // — axe's list/listitem rule needs them adjacent regardless of `display:contents`.
-    // WP-11 (CIBG markup fidelity) reworks this markup; see docs/backlog/WP-11-markup-fidelity.md.
+    // WP-11 (CIBG markup fidelity) reworks this markup; see docs/project/backlog/WP-11-markup-fidelity.md.
     a11y: { disable: true },
   },
 };